Eaton 9395 Maintenance Bypass Module Installation and Operation Manual
S
164201719 Rev 3
www.eaton.com/powerquality
5-1
Chapter 5
Understanding MBM Operation
The Maintenance Bypass Module (MBM) enables power to completely bypass and
isolate the UPS so that the UPS can be safely serviced or replaced without
interrupting power to critical systems.
The MBM consists of a maintenance bypass breaker (MBP), a maintenance isolation
breaker (MIS), an optional bypass input breaker (BIB), and an optional rectifier input
breaker (RIB). The MBP transfers the load from the UPS output to the bypass input
feeder and the MIS isolates the UPS from the bypass feed and the load. The BIB and
RIB provide a single point of rectifier and bypass input power control to the UPS and
easily removes power from the UPS for servicing.
The MBP and MIS use either electrical or mechanical (Kirk key) interlocks to prevent
paralleling the UPS inverter output and the bypass source.
5.1
MBM with Electrical Interlocks
The K1, K2, and K3 relay network in conjunction with the MBP and MIS shunt trip
circuits prevent the bypass source and the UPS inverter from being connected in
parallel.
When the UPS inverter is off (the UPS is in Bypass mode), K1 is energized. This is
accomplished by the closing of the UPS output contactor aux contacts when the
output contactor opens.
The MBP shunt trip is active when K2 is energized. This occurs when the UPS
inverter is online (K1 is not energized) and the MIS is closed.
The MIS breaker shunt trip is active when K3 is energized. This occurs when the UPS
inverter is online (K1 is not energized) and the MBP is closed.
If the UPS is online and the MIS breaker is closed and an attempt is made to close the
MBP breaker, the MBP breaker shunt trip will activate, preventing the bypass source
and the UPS inverter from being connected in parallel.
If the UPS is online and the MBP breaker is closed and an attempt is made to close
the MIS breaker, the MIS breaker shunt trip will activate, preventing the bypass
source and the UPS inverter from being connected in parallel.
5.2
MBM with Mechanical (Kirk Key) Interlocks
The Kirk key interlock system uses key-controlled mechanical locks on the MBP and
MIS breakers to prevent the bypass source and the UPS inverter from being
connected in parallel.
Two A keys and one B key are used with the MBM. A and B keys are both required to
close the MBP and the MIS.
Initially, one A key is in the solenoid lock, one B key is in the MBP, and the second A
key is in the MIS. All the keys are locked in place.
After the UPS is transferred to Bypass mode, the red light on the front of the MBM is
illuminated indicating the UPS inverter is off and Key A is removable from the solenoid
lock.
Figure
